Given they are already one goal to the good, getting a second before their opponents even have a chance to even things up would see them basically through to the next round baring a massive collapse.
Away goals are effectively worth double should it come down to the honours being even so one early goal for Liverpool would mean Besiktas would have to get three in order to progress. That is a massive ask no matter who you are or how deadly your forwards are. For Besiktas, it would be nearly impossible.
With the likes of Daniel Sturridge, Raheem Sterling and Mario Balotelli available to manager Brendan Rodgers, that should be the aim.